The invention relates to a demolding apparatus for a molding machine. Such demolding apparatuses are used in particular in the case of injection-molding machines for the production of plastic moldings, but can also be used in molding machines of other types, such as for example diecasting machines, molding presses and the like.
With such a demolding apparatus, the demolding operation proceeds as follows: firstly, the mold is opened by moving the mold halves apart. Then the gripper is made to run into the opened mold. Subsequently, the ejector carries out its ejecting stroke, so that the molding is partially moved out of the mold cavity by means of one or more ejector pins and brought into the gripping region of the gripping member, so that it can be grasped by the gripping member. Then the moving away movement is carried out by the gripper or the gripping member--in relation to the gripper--parallel to the direction of ejection, in order to release then completely from the mold cavity the molding held by the gripping member and also lift it off the ejector pins. This moving away movement of the gripper can also begin already before the ejector has reached the end point of its ejecting stroke. After carrying out the moving away movement, the running out movement of the gripper transversely to the direction of ejection can then be performed, by which the molding held by the gripping member is moved out of the mold into a position where the molding can be removed for further treatment or further transport. The various movement operations of the mold, of the gripper and of the ejector must be carefully coordinated with one another and carried out partly with time overlap, in order on the one hand to avoid time loss and achieve a high cycle rate of the machine, but on the other hand to eliminate with certainty the risk of mutual hindrance of these movements and of damage to the moving parts, even in the case of drive malfunctions.
In the case of the hitherto customary demolding apparatuses of this type, a separate drive is required for carrying out the moving away movement of the gripper or of the gripping member parallel to the direction of ejection, said drive being provided in addition to the drives for opening and closing the mold, for actuating the ejector and for the running in and out of the gripper. This drive for the moving away movement constitutes an additional constructional expenditure, which makes the overall apparatus more expensive and also more susceptible to malfunctions. The components of this drive to be fitted on the gripper or gripping member increase the mass to be moved each time the gripper is run in and out. The main problem is, however, to control the drive for the moving away movement in optimum time coordination with the movements of the ejector drive and the other drives in such a way that least possible time losses occur and highest possible cycle rates of the molding machine are possible.
In the case of drives to be activated separately, unavoidable time losses occur owing to the response times and switching times of the associated switches, signal generators and the like and to the required acceleration times.
The object of the invention is to design an apparatus of the said type in such a way that it is simplified in terms of construction and control and permits an optimum and loss-free coordination of the moving away movement of the gripping member with the ejecting movement of the ejector.
The way in which the object is achieved according to the invention is by providing a demolding apparatus for removing a molding from a molding machine. The demolding apparatus comprises a gripper for entering the molding machine when the molding machine is in a open position, an ejector for injecting the molding in a direction of injection, an ejector drive acting on the ejector for carrying out an ejecting stroke, and means for moving the gripper, or the gripping member which forms part of the gripper, together with the molding, in a direction parallel to the direction of ejection and away from the ejector. The ejector drive is coupled, at least during the final part of the ejecting stroke, to one of the gripper and the gripping member by means of a drive transmission. The drive transmission has a step-up ratio greater than one.
The invention dispenses with the need for a separate drive for the moving away movement of the gripping member, and this moving away movement is controlled by direct drive transmission from the ejector drive. A considerable constructional simplification is attained as a result. Time losses due to response times and switching times cannot occur.
Embodiments of the invention are explained with reference to the drawings in which: